1. Field of the Invention
The present invention relates to a liquid crystal display device and a method for manufacturing the same. More particularly, the present invention relates to a liquid crystal display device having a nano-polymer adhesive layer that prevents a peeling problem from occurring between a substrate and a pattern and/or between one pattern and another pattern, and a method for manufacturing the same.
2. Discussion of the Related Art
New high-tech visual display devices, such as high definition TVs are currently being developed. Accordingly, flat panel display devices have been developed to replace cathode ray tubes (CRT). The flat panel display devices include liquid crystal display (LCD) devices, electro luminescence display (ELD) devices, vacuum fluorescence display (VFD) devices, and plasma display panel (PDP) devices.
LCD devices are advantageous in that they have a thin profile, low production costs, and low power consumption. Thus, they are increasingly used in vehicles, color TVs, laptop computers and pocket computers.
LCD devices include a thin film transistor (TFT) array substrate as a first substrate, a color filter layer array substrate as a second substrate, and liquid crystal having anisotropy in a dielectric constant formed between the first and second substrates. LCD devices are operated by switching TFTs on and off using a process where sub-pixels select address lines and a voltage is applied to corresponding sub-pixels.
LCD devices are manufactured using a transistor array substrate forming process, a color filter array substrate forming process, a spacer forming process, a sealant forming process, a substrate bonding process and a liquid crystal injecting process.
Referring to FIG. 1, a method for manufacturing a related art liquid crystal display device is shown. FIG. 1 is a flow chart illustrating the method for manufacturing a related art liquid crystal display device.
In the transistor array substrate forming process (S1), deposition, photolithography, and etching are repeatedly performed on a first substrate to form transistors and pixel electrodes in sub-pixels defined by gate lines and data lines.
In the color filter array substrate forming process (S2), a black matrix layer is formed on a second substrate, red (R), green (G), and blue (B) color filter layers arranged in a designated order are formed on the black matrix layer, and a common electrode is formed on the overall surface of the second substrate including the color filter layers. To compensate for a difference in heights of the color filter layers and to prevent materials of the color filter layers from being diffused into a liquid crystal layer, an overcoat layer may be formed on the overall surface of the second substrate including the color filter layers.
After the transistor array substrate forming process (S1) and the color filter array substrate forming process (S2) are completed, an orientation film that determines an initial orientation of liquid crystal may be formed on the overall surface of the first or second substrate provided with various patterns.
After the transistor array substrate forming process (S1) and the color filter array substrate forming process (S2) are completed, the spacer forming process (S3) is performed. In the spacer forming process (S3), ball spacers, such as plastic balls or silica balls having a size of about 4-5 μm, are formed on the overall surface of the second substrate for maintaining a cell gap between the substrates.
Thereafter, the sealant forming process (S4) is performed. In this process, a sealant, which may contain micro pearl, is formed along the edge of the first substrate except for a liquid crystal inlet by a printing method for forming the cell gap. The sealant prevents leakage of liquid crystal.
Thereafter, a substrate bonding process (S5) is performed. In this process, the second substrate having the ball spacers formed thereon and the first substrate having the sealant formed thereon are aligned using alignment marks and bonded to be firmly attached to each other by hardening the sealant at a high-temperature and a high-pressure.
Although not shown, in order to cut the two substrates, which are completely attached to each other, into portions having a predetermined size, a scribe process, in which lines are formed on the surface of the substrates, and a break process, in which impact is applied to the lines to divide the bonded substrates into liquid crystal cell units, is performed.
Finally, the liquid crystal injecting process (S5) is performed. In this process, a liquid crystal layer is formed by injecting liquid crystal into a space between the first substrate and the second substrate using the liquid crystal inlet. The liquid crystal inlet is then sealed. Thereby, the related art liquid crystal display device is completed.
However, the above related art liquid crystal display device and the method for manufacturing the same have several problems.
First, a metal material, which is used to form the gate lines, has poor adhesion to the substrate and thus peels off from the substrate.
Second, when the cell gap between the bonded substrates increases due to various reasons, the spacers for maintaining the cell gap between the bonded substrates are not fixed in the liquid crystal layer and are movable in the liquid crystal layer. Thus, the spacers may not be uniformly distributed, and when the liquid crystal display device is moved, the spacers gather due to gravity.
Third, when the overcoat layer is formed on the overall surface of the substrate including the color filter layers, the overcoat layer may peel off from the edge of the substrate having the sealant formed thereon. To solve the above problems in the related art, a patterning process for removing the overcoat layer from the edge of the substrate is additionally performed. However, in this related art patterning process, a photo-etching process and an expensive exposure apparatus are additionally required. Thus, process time and costs are increased.